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Viruses and Prions - Microbiology Chapter 6

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Termini in questo insieme (21)

  • What is virology?

    Virology is the study of viruses and viral diseases.

  • Why are viruses classified as nonliving microbes?

    Viruses lack cellular structure and cannot reproduce or carry out metabolism independently, so they are classified as nonliving microbes.

  • How do viruses differ from prokaryotic and eukaryotic cells?

    Viruses are acellular, lack organelles, and depend on host cells for replication, unlike prokaryotic and eukaryotic cells which are cellular and metabolically active.

  • What are the main viral structures and their functions?

    Capsids protect viral genomes, envelopes aid in host cell entry, and spikes help attach viruses to host cells.

  • What genomic varieties are seen among viruses?

    Viruses can have double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), positive-sense RNA (ssRNA+), negative-sense RNA (ssRNA-), or retroviral RNA genomes.

  • How do dsDNA and ssDNA viruses produce mRNA for viral proteins?

    dsDNA viruses use host or viral DNA-dependent RNA polymerase to transcribe mRNA; ssDNA viruses first convert to dsDNA before transcription.

  • How do ssRNA+ viruses and retroviruses produce mRNA?

    ssRNA+ viruses serve directly as mRNA; retroviruses reverse transcribe RNA into DNA, which integrates into the host genome to produce mRNA.

  • Why do RNA viruses evolve faster than DNA viruses?

    RNA viruses have higher mutation rates due to error-prone RNA polymerases lacking proofreading, leading to faster evolution.

  • What is the difference between antigenic shift and antigenic drift?

    Antigenic drift is gradual mutation accumulation; antigenic shift is abrupt reassortment of viral genes, both affecting influenza virus evolution and outbreaks.

  • Define host range and tropism.

    Host range is the spectrum of host species a virus can infect; tropism is the specific cell types a virus can infect within a host.

  • What are the steps of lytic bacteriophage replication?

    Attachment, penetration, biosynthesis, assembly, and release of new phage particles causing host cell lysis.

  • What is lysogenic replication in bacteriophages?

    Phage DNA integrates into host genome as a prophage, replicates with host, and can later enter the lytic cycle.

  • What is phage conversion and its medical importance?

    Phage conversion is when a prophage confers new properties to a bacterium, such as toxin production, impacting disease severity.

  • What are the generalized steps of animal virus replication?

    Attachment, penetration, uncoating, replication, assembly, and release.

  • How do enveloped and naked animal viruses differ in replication?

    Enveloped viruses often enter by fusion and exit by budding; naked viruses enter by endocytosis and exit by cell lysis.

  • What is a persistent infection and its types?

    A persistent infection lasts long-term; chronic infections continuously produce virus, latent infections have periods of dormancy.

  • What makes a virus oncogenic?

    Oncogenic viruses can cause cancer by integrating into host DNA or altering cell cycle control; examples include HPV and Epstein-Barr virus.

  • What are prions?

    Prions are infectious proteins that are misfolded forms of normal proteins causing neurodegenerative diseases.

  • How do prions affect the brain and disease outcome?

    Prions cause brain damage leading to spongiform changes and are invariably fatal once symptoms develop.

  • Name prion diseases in animals.

    Scrapie in sheep, bovine spongiform encephalopathy (mad cow disease) in cows, chronic wasting disease in deer and elk.

  • What prion diseases affect humans and how are they transmitted?

    Creutzfeldt-Jakob disease and variant CJD; transmitted by contaminated tissue, medical procedures, or inherited mutations.